The present invention relates to an ignition system of an internal combustion engine, which ignites mixture gas of air and fuel such as gasoline by discharge spark and converts combustion pressure into power, and the invention relates to an ignition method of fuel charged in a fuel chamber.
As means for igniting mixture gas of air and fuel in an internal combustion engine, one which applies high voltage pulse between two electrodes and ignites the mixture gas by generated discharge spark, is frequently used.
When discharge duration of the discharge spark used for ignition and magnitude of the discharge spark are sufficient, gas molecule of the mixture gas is excited by discharge immediately after the start of discharge. Further, the gas molecule of ionized mixture gas is accelerated by electric field by discharge and collides against gas molecule of another mixture gas, which generates a plurality of ionized molecule. Therefore, the ionized molecule is exponentially increased. If the gas molecule of mixture gas is ionized in this manner, the combustion speed after ignition is increased, and combustion efficiency is enhanced.
This ignition method, however, has characteristics that airflow between the two electrode wanders, or discharge-start voltage is largely varied by existence of impurity particle. Therefore, magnitude of discharge spark and discharge duration are varied, which largely affects ignition performance of fuel, combustion state and combustion efficiency. Especially since the internal combustion engine is cold immediately after actuation thereof, combustion is not stabilized, which largely affects magnitude of discharge spark and discharge duration.
If the magnitude of discharge spark and discharge duration are varied, the number of gas molecules of mixture gas which is excited is not stabilized. Hence, the combustion speed is decreased, combustion efficiency is deteriorated, which causes an accidental fire, deteriorates fuel consumption ratio of fuel due to incomplete combustion, lowers engine output, or increases hydrocarbon compounds in exhaust gas.
Especially in a low load driving state and in a lean burn vehicle engine, output of the engine is largely lowered and thus, various ignition systems have conventionally been proposed to enhance the combustion state in the combustion chamber.
As an ignition system for the internal combustion engine which enhances the ignition performance of fuel, there are a multi-point ignition type spark ignition system and a continuous ignition type spark ignition system. Japanese Patent Application Laid-open No. 2001-82306 proposes one multi-point ignition type spark ignition system. Japanese Patent Application Laid-open No. 2001-50147 proposes one continuous ignition type ignition system.
The multi-point ignition type ignition system proposed by Japanese Patent Application Laid-open No. 2001-82306 is a system that a piston or a combustion chamber is provided at the portion of its wall surface with ceramic material which is an insulation member, a plurality of electrodes are disposed on the ceramic material. Therefore, the ignition point is increased, and mixture gas is ignited.
The continuous ignition type ignition system proposed in Japanese Patent Application Laid-open No. 2001-50147 is an ignition system that energization and de-energization of primary current to be sent to an ignition coil are repeatedly controlled to allow the spark plug to carry out a plurality of discharges.
According to the ignition system of the multi-point ignition type spark, however, since machinability of combustion chamber and piston is complicated and difficult, applicable internal combustion engine is limited. Further, when the electrode is deteriorated with time over long term usage of the internal combustion engine, it is necessary to replace the piston and combustion chamber. Therefore, there are problems that operability of replacement and repair is inferior, and operation cost is expensive.
Further, according to the continuous ignition type ignition system, since the ignition control circuit is necessary, there are problems that the ignition system becomes complicated. When the parts are replaced or repaired, the entire ignition control circuit must be replaced, which increases the costs.
It is an object of the present invention to provide an ignition system for an internal combustion engine which can be easily produced, which has excellent operability at the time of replacement and repair and which does not require high operation costs, and to provide an ignition method of fuel charged in a fuel chamber.
A first aspect of the present invention provides an ignition system for an internal combustion engine comprising a grounding electrode which is electrically grounded, a center electrode to which high voltage pulse is applied, a main grounding electrode provided in the grounding electrode, an auxiliary grounding electrode provided in the grounding electrode, and an inductor section provided in the auxiliary grounding electrode, wherein an end of the main grounding electrode and an end of the auxiliary grounding electrode are disposed close to the end of the center electrode, and wherein the inductor section is integrally provided between a portion branched from the grounding electrode and the end of the auxiliary grounding electrode.
Since the auxiliary grounding electrode includes a function of an inductor, if high voltage pulse is applied to the electrode and the auxiliary grounding electrode is allowed to carry out the auxiliary discharge, the counterelectromotive force is generated in the inductor section of the auxiliary grounding electrode. Thus, the auxiliary discharge is completed in a short time. The mixture gas in the combustion chamber is not ignited, but the gas molecule of mixture gas can be excited. There is an effect that main discharge by the main grounding electrode ignites the gas molecule of excited mixture gas, ignition is reliably carried out, and the combustion efficiency is enhanced.
According to a second aspect of the invention, in the ignition system for the internal combustion engine of the first aspect, wherein the auxiliary grounding electrode is a bar-like bent portion that the inductor section is provided between the end of the auxiliary grounding electrode and the grounding electrode.
It is possible to set the reactance of the inductor section to an appropriate value, the discharge state of the auxiliary discharge is varied, and it is possible to further enhance the combustion efficiency.
According to a third aspect of the invention, in the ignition system for the internal combustion engine of the first aspect, wherein the inductor section is a helical bent portion.
It is possible to set the reactance of the inductor section to an appropriate value, the discharge state of the auxiliary discharge is varied, and it is possible to further enhance the combustion efficiency.
According to a fourth aspect of the invention, in the ignition system for the internal combustion engine of the first aspect, wherein the auxiliary grounding electrode is extended from the end of the main grounding electrode.
By disposing the auxiliary-grounding electrode on the end of the main grounding electrode, machinability of the electrode at the time of production thereof becomes easy.
According to a fifth aspect of the invention, in the ignition system for the internal combustion engine of the first aspect, wherein a distance between the auxiliary grounding electrode and the center electrode is narrower than a distance between the main grounding electrode and the center electrode.
Since the distance between the auxiliary grounding electrode and the center electrode is narrower than the distance between the main grounding electrode and the center electrode, there is effect that the auxiliary discharge can be carried out before the main discharge more reliably.
According to a sixth aspect of the invention, in the ignition system for the internal combustion engine of the first aspect, wherein for the single center electrode, the grounding electrode is branched into the single main grounding electrode and a plurality of auxiliary grounding electrodes.
Since the plurality of auxiliary grounding electrodes are provided for one main grounding electrode, the exciting state of the mixture gas molecule can further be enhanced.
According to a seventh aspect of the invention, in the ignition system for the internal combustion engine of the first aspect, the system further comprises a plurality of sets of opposed the grounding electrodes and the center electrodes.
Since the plurality of electrodes are provided, also for an internal combustion engine having a large combustion chamber, the mixture gas is brought into excited state by the auxiliary discharge, and all of the gas can be burned by the main discharge.
According to an eighth aspect of the present invention, there is provided an ignition method of fuel charged in a fuel chamber, comprising the steps of charging fuel and air into a combustion chamber, feeding high voltage pulse to a center electrode, carrying out auxiliary discharge between an auxiliary grounding electrode and the center electrode to excite mixture gas of fuel and air in the combustion chamber, and carrying out main discharge between a main grounding electrode and the center electrode to ignite the mixture gas.
The mixture gas molecule is excited by the auxiliary discharge, and mixture gas excited by the main discharge can be ignited. Therefore, the ignition is reliably carried out, and the combustion efficiency can be enhanced.